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Chapter 14 (Genetics (homozygote (pair of identical alleles for a gene…

- - - - Phenotype,observable traits or appearance
        
        Genotype, genetic makeup
        
        monohybrid
        
        heterozygous for the one particular character being followed in the cross
        
        eye color- 1 character
        
        P generation, "true breeders"
        
        lowing two characters at the same time, allele for yellow seeds is dominant and allele for green seed is recessive
  - - - Phenotype, observable traits or appearance
        
        Genotype, genetic makeup
        
        test cross
        
        reveals the genotype of the organism
        
        crossed with a homozygous individual expressing the recessive trait
        
        dyhibrid cross
        
        individual heterozygous for the 2 characters being followed in the cross
        
        transferred as package due to location of the gene
  - - - cross between heterozygotes
- - - - heritable feature that varies among individuals
    - - variant for a charcater
  - - - alleles
      - nucleotides at a specific place
      - can affect the function of the encoded protein
    - - somatic cell in an in a diploid organism has two sets of chromosomes
      - genetic locus is represented twice in a diploid cell
    - - the allele for the recessive was a white flower
      - F1 plants had purple flowers because the allele for trait was domiant
    - - two alleles for a heritable character segregate during gametes formation and end up in different gametes
      - egg or sperm get only two alleles that are present in the somatic cells of the organism making the gamete
      - Punnet square
        
        handy diagrammatic device for predicting the allele composition of offspring from a cross breed individuals of known genetic makeup
        
        capital letter for dominant allele
        
        lower case letter for recessive allele
      - important for meiosis
  - - - over generations of self-pollination, plants have produced only same variety as the parent plant
        
        hybridization
        
        crossing of two true breeding parents
        
        F1 generation
        
        hybrid offspring
        
        dihybrid cross
        
        cross between F1 hybrids
        
        1 more item...
        
        Law of independent assortment
        
        1 more item...
        
        P generation "true breeders"
        
        1 more item...
        
        F2 generation
        
        second filial generation
        
        ratio between three purple flower to one white in the f2 generation
        
        P generation
        
        true- breeding parent
        
        Law of Segregation
- - - - Pp heterozygotes make enough pigment for the flowers to be purple, indistinguishable from PP plants
        
        Tay-Sachs disease
        
        can't metabolize certain lipids because a crucial enzyme does not work properly
        
        organismal
        
        qualifies as recessive
        
        lipid metabolizing enzyme in the heterozygotes is intermediate between activity level in the individuals homozygous for the normal allele
        
        biochemical
        
        incomplete dominance of either allele
        
        does not lead to disease symptoms, half the normal enzyme activity is sufficient to prevent lipid accumulation
        
        molecular
        
        depends on what level phenotype is analyzed
        
        normal allele
        
        child suffers from
        
        blindness
        
        degeneration of motor
        
        seizures
      - interbreeding F1 hybrid produces F2 offspring with phenotypic ratio of one red to two pink to one white
        
        1:2:1
      - the segregation of the red flower and the white flower alleles in the gametes produced by the pink flowered plants
        
        confirms alleles for flower color are heritable factors that maintain their identity in the hybrids
    - - red snap dragons crossed with white snap dragons
      - F1 hybrid have pink flowers
      - intermediate penotype results from flowers of the heterozygotes having less red pigment than the red homozygotes
  - - - MN blood group
        
        determined by codominant alleles for two specific molecules
        
        M allele (MM) have red bloods cells with only M molecules
        
        N allele (NN) have red blood cells with only N molecules
        
        both N and M molecules (MN) are present on the red blood cells with only N molecules of the individuals heterozygous of the M and N alleles
    - - Pleiotropy
        
        these alleles are responsible for sickle cell disease, cystic fibrosis, etc
        
        determines flower color and the coating on the outer surface of the seed
      - epistasis
        
        phenotype expression of a gene at one locus alters tat of a gene at a second locus
  - - - Quantitative characters
        
        not one of 2 discrete characters but instead vary in population in gradations along continuum
        
        multiple genes
      - Polygenic ineritance
        
        additive effect of 2 or more genes on single phenotype character
    - - neither allele is completely dominant
      - F1 hybrid have phenotype somewhere between those of the two parental varieties
- - - - dominant alleles cause lethal disease are rare and arise by mutation
      - dwarfism caused by a rare dominant allele
    - - degenerative disease of nervous system
      - no obvious effects until 35 to 40 years of age
      - condition is irreversible and fatal once the deterioration of the nervous system begins
  - - - lethal genetic disease in the US, striking one out of every 2,500 people of European descent
      - results in defective or absent chloride transport channels in plasma membranes, chloride ions outside the cell
      - symptoms
        
        abnormal absorption of nutrients in small intestine
        
        internal organs mucus buildup
    - - affects one out of 400 African Americans
      - caused by the substitution of a single amino acid in the hemoglobin protein in red blood cells
      - symptoms
        
        paralysis
        
        weakness
        
        organ damage
    - - heterozygous individuals who carry the recessive allele but are phenotypically normal
      - born to carrier parents
      - mating between two carriers corresponds to a mendelian F1 monoybrid,predicted genotypic ratio for the offspring 1 AA:2 Aa: 1 aa
- - - - the probability that both coins will land heads up is (1/2 x 1/2 = 1/4)
      - apply to F1 monohybrid
        
        genotype of F1 plants is Rr
        
        each egg produced has a half chance of carrying dominant allele (R)
        
        and half chance of getting recessive allele (r)
        
        same odds apply to each sperm cell produced
        
        both the egg and the sperm that came together must carry the r allele
        
        F2 plants have wrinkled seeds the recessive trait
        
        probability that that an r allele will be present in both gametes
        
        1/2 x 1/2 = 1/4 wrinkled (rr) or (RR)
  - - - prob that one possible way of obtaining an F2 heterozygote, dominant from the egg and recessive allele from the sperm is 1/4
      - 1/4 + 1/4 = 1/2
- - - - transmits nutrients and fetal waste between the fetus and the mother
      - biomedical and genetic tests can be performed on the fetal cells immediately providing results in a day or so
  - - - a karyotype of these cultured cells can also identify certain chromosomal defects
      - some genetic disorders can be detected from the presence of certain molecules in the fluid itself